英语专业八级阅读及参考答案.doc

Most earthquakes occur within the upper 15 miles of the earth's surface. But earthquakes can and do occur at all depths to about 460 miles. Their number decreases as the depth increases. At about 460 miles one earthquake occurs only every few years. Near the surface earthquakes may run as high as 100 ina month, but the yearly average does not vary much. parison with the total number of earthquakes each year, the number of disastrous earthquakes is very small. The extent of the disaster in an earthquake depends on many factors. If you carefully build at oy house with an erect set, it will still stand no matter how much you shake the table. But if you build a toy house with a pack of cards, a slight shake of the table will make it fall. An earthqua ke in Agadir, o, was not strong enough to be recorded on distant instruments, but ple tely destroyed the city. Many stronger earthquakes have paratively little damage. Ifa build ing is well constructed and built on solid ground, it will resist an earthquake. Most deaths in earth quakes have been due to faulty building construction or poor building sites. A third and very seriou s factor is panic. When people rush out into narrow streets, more deaths will result. The United Nations has played an important part in reducing the damage done by earthquakes. It has sent a team of experts to all countries known to be affected by earthquakes.